I buy and sell overseas, no problem. For ordinary individuals, even if you have to fill out the white customs form, you don't need to supply the commercial tariff info. As long as I'm paid up front and the recipient understands the shipping options and potential issues, there really is no problem. I've shipped lenses to China and bought my Linhof 6x9 from Croatia. By selling internationally, I can get a higher price at auction. By buying internationally, I can find goods that are more common in other countries.
For AK and HI I recommend flat rate Priority Mail boxes, if the item fits. Residents if those states know this is the best deal going for them for domestic parcels to and from the mainland.